We will investigate the mechanism of iron transport in microbial systems to determine if the mitochondria of eucaryotic microorganisms, such as Ustilago sphaerogena, possess a specific active transport involved in the uptake of natural hydroxamic acid chelates of iron, or siderochromes. We will examine the mechanism by which cells are able to utilize siderochrome iron for heme synthesis. The enzyme, ferrochelatase, will be studied to determine if the ionophore, ferrichrome, can serve as an iron donor when the enzyme functions under anaerobic conditions. We will also investigate the possibility that the iron of siderochromes is released by reduction to the ferrous state in a process coupled with the conversion of porphobilinogen to protoporphyrin. The possibility that covalent bonds of the siderochromes must be broken for iron release will also be investigated. The biosynthesis of natural hydroxamic acids, in particular, ferrichrome, will be studied. Emphasis will be placed on the N- hydroxylation of the delta amino group to ornithine to yield the hydroxylamino derivatives of this amino acid. We want to examine the activation of hydroxamic acid derivatives of ornithine, which are intermediates in cyclic peptide biosynthesis. We wish to answer the question as to whether cyclic hexapeptides, such as ferrichrome, are synthesized by a coupling reaction between two tripeptides or by a head to tail cyclization of a linear hexapeptide. In either case, the enzyme(s) responsible for the cyclization reaction will be investigated.